U.S. Pat. No. 4,429,990, granted to E. J. Tamary, Feb. 7, 1984, discloses a wicking structure for applying release liquid to the surface of a roller in a roller fixing apparatus. Release liquid, commonly referred to as "oil", is transported under pressure from a container to a permanent internal feed tube located inside a replaceable porous applicating wick. The feed tube and wick constitute a wicking or application roller which, when in contact with the fixing roller, is rotated by the fixing roller while it "oils" the surface. The structure has many advantages including ease in articulation and low wear on the fixing roller's surface.
The structure shown in that patent is commonly called a "rotating wick" and has been adopted commercially in a number of copiers and printers. The release liquid is delivered to the rotating wick using a pump through an oil feed line to a rotatable feed tube. The feed tube is cylindrical and has small holes drilled or punched along its elongated sidewalls through which liquid can pass. A replaceable wick surrounds the feed tube. It is installed or pulled over the free end of the feed tube. The replaceable wick is a porous structure which includes an inner ceramic porous material that is covered by a porous and heat-resistant fabric such as wool or a comparable synthetic fabric. Such a synthetic fabric is marketed by DuPont under the trademark NOMEX and is a well known capillary fabric which is resistant to heat and used for a variety of fusing system wicks.
U.S. Pat. No. 4,908,670, issued Mar. 13, 1990, shows the structure in which a ceramic inner core from the Tamary structure has been eliminated by using a NOMEX wrap of one or two layers directly on the distribution tube. See also, U.S. Pat. No. 3,964,431 which also shows an internally fed structure, but in which the outer material is a soft porous material such as foamed silicone rubber.
The wool, NOMEX or other fabric wraps on virtually all prior commercial rotating wicks have worked well for many applications. However, for some applications, the fabric rolling with the fusing roller leaves the pattern of the fabric in the oil coating of the fusing roller. This can cause a pattern on the receiving sheet which is especially noticeable in transparencies. Low areas of oil can also cause insufficient release causing a pickup of toner by the fusing roller. This, of course, disturbs the toned image on the sheet and in time causes wear to the fusing roller.